Bond and Flexural Behavior of Sea Sand Concrete Members Reinforced with Hybrid Steel-Composite Bars Presubjected to Wet–Dry Cycles

In this paper, accelerated tests are conducted on the bond performance of steel fiber–reinforced polymer composite bars (SFCBs) with sea sand concrete and the flexural performance of SFCB-reinforced sea sand concrete beams after conditioning in a simulated seawater wet–dry cycling environment for 30, 60, and 90 days. The beams are coupled with a sustained load during conditioning. The steel bar pullout specimens and steel bar–reinforced sea sand concrete beams are conditioned in the same environment for comparison. Overall, 24 direct pullout specimens and eight beams are tested. The test results indicate that the maximum bond stresses of the SFCBs improve after wet–dry cycling, whereas the average bond stresses at 0.05, 0.10, and 0.25 mm of free-end slippage decrease slightly. Both the maximum bond stresses and the average bond stresses at 0.05, 0.10, and 0.25 mm of free-end slippage of the steel bars decrease. No significant changes occur in the characteristic loads of the steel bar beams during the aging period, whereas the characteristic loads of the SFCB beams decrease. Residual deflections after unloading increase the flexural stiffness and energy ductility of all the conditioned beams. The crack widths of the steel bar beams significantly increase after conditioning, but these increases are not obvious for the SFCB beams.